X2-280x+2400=0

Solution for X2-280x+2400=0 equation:

X2-280X+2400=0

We add all the numbers together, and all the variables

X^2-280X+2400=0

a = 1; b = -280; c = +2400;
Δ = b2-4ac
Δ = -2802-4·1·2400
Δ = 68800
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{68800}=\sqrt{1600*43}=\sqrt{1600}*\sqrt{43}=40\sqrt{43}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-280)-40\sqrt{43}}{2*1}=\frac{280-40\sqrt{43}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-280)+40\sqrt{43}}{2*1}=\frac{280+40\sqrt{43}}{2}
$